Originally Posted by
SCChris
It means there are 3 first class seats of which they are willing to sell 2 of which as 'A' fares (generally as YUP's or mileage upgrades).
To further elaborate:
F = full fare F seats.
A = discounted F seats (YUPs), F seats for people traveling on first class round-the-world tickets, and F seats used for passengers upgrading from Y on 2-class flights, and from J on 3-class flights, using either miles or VIP upgrade certificates.
P = more deeply discounted F seats (usually KUPs).
Z (a "hidden" fare class not viewable on seatcounter) = F seats available for award travel.
A, P and Z are all subsets of F.